This invention relates generally to burners for gasifying powdery fuel materials and, more particularly, it relates to a burner for use in a gasifying reactor operating under a pressure up to 50 bars and combusting brown coal powder and a carburation fluid for producing pressurized coal gas.
Known devices, generally known as burners, for feeding mutually separated streams of powderized fuels and carburation agents into a gasification chamber, have the common feature that the powdery fuel is fed through a center tube axially arranged in the burner. As a rule one or more concentric tubes are so arranged about the central pipe as to form annular channels between each other. These annular channels serve for feeding one or more carburation agents or a mixture of carburation fluids into the reaction chamber. The outlet opening of these channels into the reaction chamber has either an annular cross-section or has the form of a plurality of bores terminating the annular channels and discharging the carburation fluid for reaction with the central jet of powdery fuel.
The feeding of powdery fuels such as brown coal dust into the central burner tube having a circular cross-section is technically simple solution. From the experience the fluidized brown coal dust can be relatively easily fed through smooth and straight tube of uniform cross-sectional area and when considering the specific conditions of the powdery material relatively high density of the dusty jet can be achieved. In known actual experimental plants (for example of U.S. Bureau of Mines Morgentown), as well as from the patent literature (for example German published application No. 2,536,249, U.S. Pat. No. 2,702,744, DDR Pat. No. 127 904) the principle of the central feeding of the fuel to be gasified into the burner is employed. A substantial disadvantage of the central discharge into the reaction chamber of the fuel to be gasified and of concentrically arranged discharge means for the carburation medium such as for example oxygen, is in the fact that due to the recirculation of the generated gas in the reaction chamber the latter is prone to mix up with the carburation medium provided that the latter is not shielded against the recirculating coal gas by means of an additional steam screen. As a consequence of this mixing action, a part of the incoming oxygen is consumed for oxidation of the combustible recirculating coal gas. In the pressurized combustion of the dusty fuel it is of advantage when the entire amount of the carburation oxygen participates in the reaction with the fuel dust and also from the economic point of view it is of advantage when the undesired marginal reactions of the oxygen are eliminated.
Another disadvantage of the feeding of the entire quantity of the coal dust to be gasified in the reaction chamber by means of a single feeding pipe which for technical reasons is symmetrically arranged in the center of the burner occurs in the event of a momentary discontunity of the feeding of the coal dust whereby the operational safety of the plant is lowered. Whereas, in general the feeding of a gaseous carburation medium in the form of a continuous jet can be insured, the supply of a fluidized dusty fluid frequently exhibits irregularities as far as the density of the stream is concerned. As a result, due to considerable variations in the coal dust supply at the exit of the burner there is the danger that the burner and the reaction chamber may become damaged, provided that the corresponding oversupply of oxygen is not immediately reduced in concert with these variations.